CiDRA GVF-100 Gas Volume Fraction Monitoring System - Manual (Page 83)

Copyright © 2006 CiDRA Corporation Page 10-9
20639-01 Rev 03
same number as described above for the ‘no flow’ condition. When
the number of consecutive bad readings is exceeded, the output will
blank (-----) and the 4-20mA output will be set to the ‘Out Of Range’
state. The second is for spurious in-range calculations of good
quality. These will manifest themselves as a positive or negative
spike of a magnitude much greater than the steady state deviations.
This filter will monitor the rate of change of the calculated value for a
number of consecutive readings. If a single reading exceeds the
desired rate of change, the transmitter will hold the last value. The
rate of change limit is a user programmable value entered in units of
percent of total transmitter speed of sound operational range (typically
4950ft/sec). If the rate of change is exceeded for three consecutive
readings, the filter will be reset and the calculated value will be
displayed.
State : Used to ‘Enable’ or ‘Disable’ the Spike Filter.
Length : Defines the number of consecutive measured points that
must be within the reading-to-reading variation range defined by the
‘Percent’ parameter in the filter setup.
Delta : Defines the reading-to-reading variation limit. This is in units
of percent of transmitter operating range.
Therefore, Reading-to-Reading Variation (RV) is the device Maximum
Measurable Value (MaxMV) in ft/sec minus the device Minimum
Measurable Value (MinMV) in ft/sec times the percent of the
Measurable Range ‘Percent’ (MR) input by the user to be used for the
filter; or:
RV = [(MaxMV – MinMV) * MR]
For example, in a device with an SOS MaxMV of 5000 fps and SOS
MinMV of 50 fps and a %MR of 10%, reading variations greater than
495 fps will be rejected.
RV = [(5000 – 50) * 0.10] = 495 fps
Therefore, measured points that have measurement variations greater
than 495 fps will not be displayed or outputted until the number of
consecutive readings that do not vary by more than RV is greater than
that set by ‘Length’.
10.1.3 Input Config
The Input Config menu is used when optional external sensors (for
example a pressure or temperature transducer) are powered by and
input to the transmitter. The transmitter does not have the capability
to display or transmit these sensor values. Note: When these sensor
inputs are used the ’Temperature Sel’ and ‘Pressure Sel’ menu
options under the ‘Basic Config’ menu must be used to designate
which sensor input is used for a particular measurement.